Recently, various types of speech recognition services have been provided from smart terminals, such as iPhone, Android phone, and the like, For example, services, such as placing a call or searching web using speech, converting speech into SMS, and the like, have been provided. The speech SMS conversion services based on a server-client among these services are services that allow a smart terminal to deliver speech to a server through a network in real time when a user of a smart terminal utters speech to be converted into characters and a speech recognition server to recognize speech signals, convert the recognized speech signals into characters, and transmit the converted results to the smart terminal.
In order to provide the speech recognition SMS conversion services based on the server-client, there is a need to operate a large-scale speech recognition server. Therefore, most of the major portal enterprises that mainly provide the services provide the services free of charge for entering a nascent market. It is expected that a demand for speech recognition services has been increased in future, which results in increasing maintenance costs of the services. Therefore, it may be difficult to continue to provide the speech recognition services free of charge. As a result, in order for the enterprises providing the services to generate revenue, it is expected that the enterprises add advertisements to the speech recognition SMS conversion services. However, most advertisements are exposed as spam advertising independent of the user's intention, which may lead to degradation in a service use frequency of a user.